A battery fire in an electrical device aboard a United Airlines flight forced a Newark-bound plane to turn back to San Diego on Tuesday, leaving four people hospitalized, officials said.

The crew aboard United Flight 2664 prevented the fire from spreading further, and the aircraft returned to the airport, according to a Twitter post by the San Diego Fire Department.

Emergency personnel were deployed and are currently treating passengers, San Diego International Airport spokeswoman Sabrina LoPiccolo said in a telephone interview with CNN .

Data from FlightAware shows that the aircraft, a Boeing 737 MAX 8, took off from the airport at 7:07 am Pacific Time and landed in San Diego at 7:51 am.

Firefighters assessed all passengers and crew, and four people were taken to the hospital. Two others refused further treatment, according to another tweet from the San Diego Fire Department.

US Federal Aviation Administration (FAA) spokesman Ian Gregor told the CNN that the fire was from a laptop battery. “The FAA will investigate,” said Gregor.

Flight attendants responsible for containing the fire were among those taken to hospital, according to the airline.

“Our crew acted quickly to contain the device and medical staff attended to the aircraft upon arrival at the gate,” United Airlines spokesman Charles Hobart said in a statement. CNN .

“Several flight attendants were taken to the hospital as a precaution and two customers were assessed on site,” he said.

“We thank our crew for their swift actions in prioritizing the safety of everyone aboard the aircraft and we are taking steps to get our customers to their destinations,” added Hobart.